This disclosure relates to a system and method which deposits deck material on a beam structure, processes the deck material and stud welds shear connectors (known as “studs”) onto bare beams or through the deck material to the beam and scientifically analyzes weld parameters, such as time, current, lift and plunge, used during the stud weld process. In particular, the present disclosure relates to a plurality of carts which efficiently deposits the deck material to the beam structure, and welds the studs onto bare beams or through the deck material while analyzing the stud weld at the weld site and while allowing the tradecraft worker to remain standing in an unbent position while working during these processes. The carts of the present disclosure either independently or in combination provide a new way to process deck material, to weld stud shear connectors and to scientifically analyze and report on each welded stud.
The beam structure (FIG. 1) includes beams for construction including but not limited to buildings and bridges. The beam structure may also include girders. The deck material relates to floor decking that is connected to the appropriate beam structure wherein the floor decking is configured to hold poured concrete that eventually forms a floor for the beam structure and eventually for the beam structure's intended use such as a building floor. Typically, the floor decking comprises a metal deck having sequential peaks and valleys.
During construction of a building, structural steel beams are first set into place and bolted together to create a framework, or skeleton, for the desired structure. In laying the floor decking, an operator lifts bundles of metal deck sheets to the workers and places the bundles on top of the bare beams or girders, wherein each bundle is approximately two to three feet wide and ten to thirty feet long. Multiple workers then break the bundle of metal deck sheets, pick up one sheet of metal deck and start walking across the open areas of the framework to lay the sheet of metal deck onto the beam. Workers then lay additional metal sheets across the beams and manually “puddle” weld the metal decks to the beams to create the form for the later poured concrete floor. The “puddle” weld comprises a temporary weld to attach the metal deck to the beams. Typically, the workers laying out the metal deck outpace the workers that are puddle welding the metal deck resulting in workers walking across loose metal deck sheets.
The workers may need to cut the metal deck to fit around certain openings or weld the metal deck to the steel beam. The workers require a tank cart to assist in cutting the metal deck. These tank carts secure and transport the necessary cylinder tanks such as acetylene and oxygen tanks. Due to the peaks and valleys of the metal deck and the configuration of the wheels of the tank cart, the wheels are not uniformly positioned across any one set of peaks and valleys. As such, the worker has to tilt the tank cart (typically 150-300 lbs.) toward him/her and move the unbalanced weight caused by the wheels being on different planes of the metal deck floor. As the worker pulls the weld cart perpendicular to the peaks and valleys of the metal deck, a constant up and down jarring force applies to the weld cart and/or the worker. This force can lead to unsafe working conditions such as injured backs or toppled cylinders. To compensate for the awkward moving of the cart, the worker may choose to add costly extension hose to the cart in order to limit movement of the cylinders. The additional hose is expensive, costly to repair and may provide a trip hazard. Damaged hoses may also warrant expensive fines from safety organizations.
Once the worker welds the metal deck to the beam or girder, the metal deck hides the location of the center of the actual underlying beam or girder. The welded deck also hides the condition of the top flange, or weld base of the steel, which may be covered with rust, mill scale, over spray and even paint, which are weld contaminates and are not allowed under standards of the American Welding Society. The applied deck also provides an area for moisture, water, snow and possibly ice to collect, these environmental effects also being contaminates not allowed by the American Welding Society. The workers laying the deck and the workers cutting the deck to fit and the workers puddle welding the deck typically complete a large area of hundreds if not thousands of square feet of deck before the workers begin stud welding the deck. In order to find the optimum stud weld area, which is the center of the beam or girder, the worker may then have to deform the deck in two directions to profile the location of the underlying and invisible beam. As shown in FIG. 2, the worker bends over and applies a hammer to deform the metal floor deck. Although the metal floor deck has been specifically designed to safely support a load, the worker physically deforms this designed metal deck to locate the beam.
Based on the deformation of the deck, the worker then lays a chalk line that represents the center of the underlying beam and the optimum location on the beam to weld the desired number of stud shear connectors. After the worker marks the underlying beam, the worker dispenses ferrules in the valley of the deck, along the chalk line on top of the deck by bending over to individually deposit each ferrule. At the same time while bent over the work surface, the worker properly orientates the ferrule in the valley of the floor deck. This process is repeated to place each stud, while bent over, and then to move the stud welding equipment in-place and to weld each stud. All of this is performed from the bent over position while attempting to walk safely across the corrugated floor deck which may typically have a mere five inches wide high and a seven inches wide valley. The valley is two inches to three inches below the high or peak of the deck.
During construction, the shear connector studs are commonly used to improve shear strength in concrete slabs of the structural framework. The studs transfer horizontal shear from steel beam to concrete slab, causing them to act as one. Greater strength and stiffness increase live load capacity so that as much as thirty-five percent less steel may be used to build the structural framework.
The studs can be welded directly to the beam of the structure or can be welded through the metal deck that is connected to the underlying beam or girder of the structure. An arc welding process, such as drawn arc welding, is often used to make these weld connections. Stud welding is an accepted form of electric arc welding in which a stud welding system welds the studs to the base structural components (i.e., through the metal deck and in contact with the beam). During this stud welding process, the stud gun generates an electric arc between the stud and the base metal component and that arc is automatically timed and the current is controlled at the welding power source in order to melt the end of the stud and a portion of the base metal component, i.e., metal deck or beam/girders. The amount of lift (the optimum distance the gun draws the stud back during the weld process to receive the perfect arc), the proper weld current, the length of time the current is being drawn and the plunge (how much stud is melted and how far the stud travels into the weld zone) are all critical measurements in order to receive a 100% cross sectional and a AWS approved weld.
During the welding process, the ferrule shields the arc as the arc combines the molten components of the stud and base metal component. The ferrules concentrate weld heat between the stud and the work surface and contain the molten pool of melted metal around the base of the stud. As such, the ceramic ferrules play a critical role in weld quality by shielding the arc, confining molten metal and minimizing oxidation of the weld. As the arc shuts off, the stud is plunged into the molten components by springs of the stud gun, and the weld is formed as it cools.
After positioning the ferrules, the worker must bend over at each ferrule to place and orientate a stud shear connector to be picked up by the worker doing the welding at a later time. The same stud shear connector will again be picked up by the same worker or another worker during the stud welding process and loaded into the stud gun. But first, the worker must place the welding gun and cables near each ferrule and stud and pick up the stud lying on the floor and load it into the gun. The worker will then place the loaded stud into the ferrule. The worker then welds each stud to the top flange of the underlying bare beam or through the deck material while remaining in the bent position. This process results in repeated bending over to dispense ferrules and studs, move the equipment, load the stud into the weld gun and to stud weld the stud to the bare beam or through the floor deck. As such, this process is extremely time-consuming and physically demanding. While bent over and welding, the worker's face is in a close proximity to weld gases caused by welding galvanized material and hot weld splatter that may easily extend twenty-four inches from the weld zone.
Although ferrule applicators may reduce the physical stress of placing the ferrules, the worker's back is still subjected to repeated physical stress of placing each stud at the weld site, moving the equipment and cables to each weld site and welding each stud to the bare beam or through the floor deck. As the process is physically demanding, the weld may not be a quality weld due to operator movement during the weld, resulting in error at the weld zone. Additionally, as shown in FIG. 2a, workers weld ¾″ diameter studs next to ⅝″ diameter puddle welds, in many if not all instances, leading to duplication in labor, time and equipment to puddle weld and then subsequently stud weld the floor decking.
As shown in FIG. 3, the worker bends outside of the safety fence in order to access the ferrule and to stud weld the stud through the floor deck. The National Safety Counsel reports that back injuries are the number one occupational safety hazard in the United States. Back injuries are also the number one reason for worker compensation claims and usually the most costly per incident. Furthermore, as shown, tools, cables, hoses and wires are positioned on the floor deck in an unsafe manner. The unsuspecting worker, who is already hanging outside of the safety cable, is unaware of the recently created trip hazard at the perimeter of the building.
Presently, a method of testing the studs is to destructively bend test a sample stud and ring test the other studs. Both methods are non-scientific and subject to an individual's interpretation. Additionally, there is no present method in practice or of scientific value to check “puddle welds” or “deck welds” for securing the metal deck to the top flange of the beam or girder. These stud tests (or in the case of no tests for deck welds) do not scientifically check each weld at the weld site in real time. The “bend” and “ring” tests comprise the worker hitting the welded stud with a hammer to look for damage to the weld zone and to listen for a particular tone. Although there are presently time/current analyzers built into transformers of some high-end welders, these welder are typically 50′ to 300′ from the weld site. These welders provide the worker the results of time and current for each weld at the transformer on the ground floor, but because the results are not displayed at the weld site, which is possibly hundreds of feet away from the transformer, they are of no “real time” or value added benefit.
At the end of the day a report may be generated regarding time and current for each stud, but since the studs are not numbered, the report will merely tell you of the time and current of each weld and the number of suspect welds “somewhere” on the deck. Since the worker and his equipment have moved on, there is no real value added by present time/current analyzers. Additionally, there is no current method for scientifically reading the four critical parameters of time, current, lift and plunge of the weld, during the weld and immediately reporting the results to the worker, in real time, at the weld zone so the worker may verify the quality of the weld and test the stud if the weld is reported outside of desired weld parameters.
Engineers, however, design the beam structure and deck material for proper loading and design configurations. The use of stud shear connectors eliminates 20%-35% of the normally required steel. Once the designed beam structure and metal deck are set/positioned/supported, workers, however, physically deform these designed beam structures and metal decks in order to find the center of the hidden beam in order to obtain the optimum welding location. The physical determinations, however, for locating the underlying beam and for testing the welded stud damage the properly designed beam structures and metal deck.
Accordingly, current deck processing procedures are in need of a safe and ergonomic procedure to: transport and position floor decking; transport and position oxygen and acetylene tanks; weld the deck to the beam so that it may be scientifically tested; transport equipment such as stud welders and battery charging equipment for hand tools; eliminate unorganized equipment hoses, wires and cables; weld studs onto bare beams or through the deck material and conduct quality control tests for the welded studs in real time and at the weld site.